As a parish priest at Mass with ubiquitous distribution of the "cup" I find it repugnant to be consigned to finish off the dregs from the imbibing communicants. I henceforth refuse in conscience because it is most contrary to the most august Sacrament of the thrice holy Body and Blood of the Lord that his purity and sweetness should be reduced to such degrading filth. Who is to purify the vessels after the common cup in order to avoid this dilemma?
One obvious solution (thought of long ago by our holy forebears) is to eliminate the common cup altogether (communion by intinction being a fine sanitary way to provide both species)! However, sometimes we priests are placed in situations where we cannot reasonably accomplish that and are left with cup in hand.
As celebrant one can (though against the norm) leave the purification of those vessels for after the Mass and have the diluted contents of the purification deposited in the sacrarium (or directly in the earth where there is no legitimate sacrarium). Alternately, one might delegate the extraordinary minister of Holy Communion to consume the remainder and purify. Ideally, perhaps, the last person in line (since those partaking the common cup obviously have no problem drinking after strangers) would finish the contents.
I, for one, refuse from this day forward to communicate this lipsticked, back-washed potion of disgust, in reverence of our Most Blessed Lord--the Most Blessed Sacrament. The Most Blessed Sacrament ought not be the Most disgusting! It ought not be disgusting at all, especially for the Holy Priests of God. Shall we call it a double sacrilege to desecrate the sacred species in this way of distributing and in forcing the priests who find it repugnant to participate in it? Bishops and pastors need to examine their consciences here. Just one more reason to eliminate the abuse of the ubiquitous "communion cup".